Wheel dressing tool and method for making the same



July '16, 1946.

W. LUDEL WHEEL DRESSING TOOL AND METHOD FOR MAKING THE SAME Filed June 28, 1944 INVENTOR Willzlzm lamb'el.

AZIATTORNEY Patented July 16, 1946 TOOL AND METHOD FOR ,WHEEL DRESSING NT OFFICE:

MAKING THE SAME William Ludel, New York, N. Y. Application June 28,1944, Serial No. 542,525

This invention relates toan abrasive wheel dressing tool, more particularly to an abrasive wheel dressing tool employing diamonds as the wheel dressing abrading material and to a method for preparing the same,

Known to me is the provision of tools employing diamonds for dressing grinding wheels where these. are made of .Carborundum or like material in which the abrasive particles of this constitution are united by some bond or binder and are formed o1- cast into wheels, When these wheels become scored or otherwise irregularly worn, they are ,dresscd, by a dressing tool, as known in the art, in which a toolcarrying a harder material than, the-abrasive of the wheel is employed to refinish the surface.

7 There has been devised, as known to me, dressing tools'comprisinga rod-like member formed at one end with a cup or socket within which diamond'dust or diamond fragments are held by a matrix of alloy. The cup or socket is filled either bypouring. the mixture of molten metal and the diamond dust into the cup or socket, or by molding a'mixture of the diamond dust and pulverized alloying material to form, under sintering temperatures, a bond for the diamond dust particles, thereby providing a formed abrasive material by the combined action of heat and pressure. These dressing tools have not met with success due to an inefiicient use of the diamond dust or particles. Use of these tools has resulted in glazing of the dressing tool surface, tending to favor the use of a single large diamond for the dressing operation and more frequently employing a cluster of a small number of diamonds in some mechanical holder to effect the wheel dressing operation. a

The prior procedureknown to me involving a pouring of a mixture of alloying material and diamond dust or particles or the molding process is not efficient-because of the haphazard arrangement of the diamond dust, the failure to take into account the weakness-of diamond fragments and the reliance merely upon the characteristic hardness of the diamond dust or fragments in relation to the abrasive of the wheel to be dressed.

I have discovered that within limited and rather critical sizes of diamond crystals of octahedron shape and alloying material, which will hereafter be described more particularly, and which may be heatedto secure a free-flowing, extremely -liquidmaterial, that a more efficient wheel dressing tool may be made than heretofore. I have discovered that diamonds of octahedron 3 Claims. (01. 125-39) shape inan, alloyat the liquid stage adjust themup selves in a more efficient abrading position, espe# cially under heat treatment tending to effect ebullition of the alloy.

Still more particularly I have discovered that with diamonds of a size within specified ranges and of octahedron shape, an ebullition of the matrix alloy free from exterior influences tending to otherwise stir up the liquid mass, causes the particles of diamond of octahedron shape to adjust themselves, prior to setting of the alloying matrix, to produce a highly efficient wheel dressing tool. v

Accordingly, it is an object of my invention to provide a wheel dressing tool employing diamond crystals held in a wheel tool by a metallic matrix to dispose the crystals of diamondsto provide a highly efficient wheel dressing surface or mass, Still further it is an object of my invention to provide a method for forming a wheel dressing tool in which diamond crystals are embedded in.

a metallic matrix under conditions which will permit the diamond crystals to arrange themselves freely and assume positions within the matrix most effective for wheel dressing operations, unaltered by the means to heat the matrix metal, and uninhibited to move to have the crystals assume the most effective cutting position by contact with adjacent crystals.

Thus, it is an object of my invention to provide a tool holder with a cup or socket for exposing a wheel dressing surface or end, in which diamond crystals are held within a matrix of metallic alloy in which the particles assume the most effective cutting position by freedom of movement within the matrix alloy by melting the alloy, before cooling,.to an extremely liquid condition.

Still further objects of my invention reside in the provision of a wheel dressing tool which is highly efficient in its wheel dressing action,

To obtain these objects and such further objects as may appear herein or may be hereinafter pointed out, Imake reference to the accompanying drawing forming a part hereof in which:

Figure 1 is a side elevation partly in section diagrammatically illustrating the apparatus for forming my wheel dressing tool;

Figure 2 is a magnified fragmentary section of the working end thereof;

Figure 3 is a plan view of the working end of my wheel dressing tool; and

Figure 4 is an end elevation showing the tool applied for grinding wheel dressing operations. In accordance with my invention, by reference to the drawing, I provide a tool holder body lil which is preferably a rod of cold rolled steel of suflicient length to serve for manual holding or tool rest mounting, one end of which is restricted at l l and formed with a socket or cup I2, defined current suitable for inducing suflicient heat toconvert the matrix alloy to extrem fluidity withinthe socket I2 of the tool holder body It. In this position I then insert a strip or filament of alloying material 20, which, at the temperature of the induction heating apparatus, serves to melt a small portion thereof to provide a layer 2| of molten alloying metal. metal 20 is removed and there is added to the socket l2 a few crystals of diamond particles 22. Thereupon the strip of alloying material 25} is reinserted within the socket l2 to provide another layer of molten material. Another layer of diamond crystals 23 are then sprinkled within the socket. 'This procedure is continued to supply alternating layers of the alloying metal in molten form followed by a sprinkled layer 24 of diamond crystals until the socket it has been filled, such as by providing another or super- -imposed layer of diamond crystals 2 5.

Thereupon-the induction heating element is brought into play to bring the alloying metal to extreme fluidity to the point where there is evidence-of ebullition. During this operation the diamond crystals are free to move and in instances show evidence of rising and falling with-- in the liquefied alloy. During this action the par- 'ticles adjust themselves to position the effective cutting edges 25 in the direction of the rim 13.

A rather sparse supply of diamond crystals, to

the point where .there is sufficient space for free and independent adjustment of the crystals in relation to the liquefied alloy matrix, is one of the desirable phases of my procedure whereby the crystals may adjust themselves and assume the most desirable position for the wheel dressing operation.

In the practice of my invention, I have discovered that diamonds in the crystalling form and of substantially true octahedron shape, provicle the most desirable result and these crystals are carefully selected from diamonds as mined to be free from fracture or. chips and are therefore distinguishable from diamond dust or chippings, flakes, or the like, which are by-products of the diamond industry in connection with brillianteering or polishing diamonds for their ornamental and optical properties. In connection with atool holder which exposes a working surface adjacent the periphery ll? of approximately three eighths of an inch in diameter, I have found that in relation to the particular alloy which I will describe hereafter, that selected diamond crystals of octahedron shape and of the size approximately 25 to 35 to the carat, prefer- Thereupon the strip of.

' one of its phases.

much above 25 to the carat or much below 35 to the carat do not respond favorablywith the alloy I will now describe. s

The alloy which I have found as having a 7 specific relationship to the diamond crystals of the size as described, is an alloy made under the patent to Leach, Patent No. 1,829,903, assigned to alloy starts to melt at about 1,185 F. (641 C.)

and is extremely liquid and free-flowing at 1,300 F. (704 C.) to 1,340 F. (727 0.). v

At temperatures somewhat higher than 1,340" F. (727 0.) there is evidence of ebullition, which is to be noted in connection with my process in The characteristic features of the alloy described in relation to the diamond crystals resides in the extreme fluidity and freeflowing character of the alloy at the temperatures induced by the induction heater and the evidence at higher temperatures of ebullition.

Extraneous disturbing influences are avoided by the induction heating method which I have described, which, by reason of the method of adding the diamond crystal in their relatively sparse condition'and the fluidity of the alloy, serves'to permit the particles to assume a position during heating to dispose and position the sharper points 26 in the direction of the working edge l3 as the tool'holder body I0 is held vertically during the heating operation. The pyramidal side walls of the diamond crystals are likewise effective as the diamonds wear down in the wheel dressing operation as shown in Figure 4 Where the tool I0 is pressed against the periphery ofthe grinding wheel W. 2

Upon: cooling of the tool and its contents, the alloy matrix retains the diamond crystals in the most effective position described. This effect is sharply in contrast with methods heretofore knownto me, involving either the pouring of a molten alloy and diamond particles to Within the tool holder cavity, a molding mixture of the diamond'alloy and sintering of the matrix alloy, or a setting of the diamonds in a matrix binder alloy. Freedom of movement of the particles in the matrix alloy in thefluid condition contributes to the adjustment of the particles, to achieve the most desirable and effective direction and is not to be confused with a heating of a matrix alloy which merely fills and flows into the interstices of a socket filled with diamond dust or particles.

By the use of the induction heater which I have described and preferably employ, alteration by oxidation of the alloying material, is substantially avoided. The formation of an oxidized coating is likewise not experienced which, in accordance with prior methods, I believe, inhibits the free movement of the particles to their most effective abrading position.

While, frommy experience, the Sil-Fos alloy has been found to give the most satisfactory results, it is clear that other alloys may suggest themselves to those skilled in the art from some of the comparable properties during the heating operation which I have described by reference to Si'l-Fos. However, I have found that the silvercopper-phosphorus alloy which I employ additionally responds desirably during the wheel dressing operation, in that there is a kind of softwalls i i are worn down in the finishing-operation.

I maintain the induction heater in operation during the building up of the batch within the socket I 2 and my method of maintaining a liquid condition of the matrix alloy as each layer of diamond crystals is added avoids any tendency to fracture the diamond, such as is known to result by successive heating and cooling of the matrix alloy to embed diamond dust or crystals in wheel dressing tools by a procedure amounting to setting of the diamonds in the alloy and involving building up layers of alloying material, then setting diamond dust therein by removing the source of heat, followed by alternate steps of adding an additional layer of alloy and diamond dust. Each step of removing the heat by this process known to me has a deleterious effect on the diamonds due to shrinkage and expansion of the heated alloy.

The number of diamonds employed within the socket is dependent upon the size of the wheel dressing tool and the particles are limited substantially to provide the degree of sparseness and spacing of the crystals in relation to each other whereby free movement is permitted to effect the adjustment of the crystals within the fluid alloy matrix during heating operation.

The diamond crystals to be employed are those Which are free from extraneous minerals on the surfaces thereof. Mechanical cleaning may be resorted to, though frequently dipping in acids to remove extraneous matter is found to be practiced by the suppliers and is found to be desirable. While this special treatment is practiced, it is to be understood that cleanliness to insure direct contact of the alloy with the diamond crystal is the object to be attained by the cleaning process.

By my method, whereby diamond crystals or grains of octahedron shape within the range of sizes between 25 to 35 to the carat, preferably 30 to the carat, an unpredictable relationship to the preferred alloy, which I have described, exists, in that the crystals assume a desirable position in relation to the working surface and are not subject to any differential and detrimental shrinkage force in cooling of the alloy until the final mass has been formed and the finishing tool is free from any evidence of inadequate surface contact between the matrix and the diamond crystals.

Furthermore, by the use of the alloy constituent for the matrix as herein described, a fast grinding wheel finishing operation is exhibited by my finishing tool, free from any tendency to gather detritus limiting the cleaning-up action of the dressing tool in its action upon the grinding wheel.

While I do not wish to be restricted to the following explanation, the procedure described shows evidence of orientation of the most effective cutting points of .the octahedron crystals in the direction of the working surface by a flotation of the crystals in the matrix during the heating operation by the induction heater and this orientation is aided to some extent by the ebullition during the final heating steps of the filled socket after the successive layers of molten alloy and crystals have been built up to fill the socket.

Accordingly, I have provided a wheel dressing tool comprising a plurality of diamond crystals oriented with their most effective cutting edges in the direction of a working surface of the. wheel dressing tool and held therein in an alloying matrix. Other advantages will readily appear to those skilled in the art.

Having thus described my invention and illustrated its use, what I claim as new and desire to secure by Letters Patent is:

1. The method of making a wheel dressing tool in which a plurality of diamond crystals are bonded by an alloy matrix within a form, the steps which include providing said form with a charge of diamond crystals and an alloy consisting of silver varying from about 10% to 25%, copper varying from about 67% to about 88%, and phosphorus varying from about 2% to about 8%, the diamonds being sparsely distributed, and heating said alloy with the diamond crystals in situ to the point where the alloy becomes highly liquid and free-flowing to the point of fluidity, permitting the crystals to adjust themselves in the liquid alloy independently of each other, and then cooling the mixture in the form.

2. 'A wheel dressing tool comprising a body portion having a socket at one end filled with a mixture of diamond crystals and a matrix alloy, the diamond crystals being sparsely disposed and independently oriented in the direction of the mouth of the socket, said diamond crystals being approximately 30 to the carat and the alloy matrix consisting of silver varying from about 10% to 25%, copper varying from about 67% to about 88%, and phosphorus varying from about 2% to about 8%. i

3. A wheel dressing tool comprising a body portion having a socket at one end filled with a mixture of diamond crystals and a fused matrix alloy, the diamond crystals being sparsely and independently oriented in the direction of the mouth of the socket, said diamond crystals being of a size varying from about 25 to 35 to the carat and the alloy matrix consisting of silver, varying from about 10 to 25%, copper varying from about 67 to 88%, and phosphorus varying from about 2 to 8%.

WILLIAM LUDEL. 

